Hydrocracking catalyst comprising a beta zeolite and a group VB element

ABSTRACT

The invention provides a hydrocracking catalyst comprising at least one mineral matrix, at least one beta zeolite, at least one group VB element or at least one mixed sulphide phase comprising sulphur, optionally at least one group VIB or group VIII element, optionally at least one element selected from the group formed by silicon, boron or phosphorous, and optionally at least one group VIIA element.

The present invention relates to a catalyst for hydrocrackinghydrocarbon feeds, said catalyst comprising at least one amorphous orlow crystallinity oxide type matrix, at least one element (metal) fromgroup VB (group 5 in the new notation of the periodic table: “Handbookof Chemistry and Physics”, 76^(th) edition, 1995-1996, inside frontcover), preferably niobium, at least one beta zeolite, at least onepromoter element selected from the group formed by boron, phosphorousand silicon, optionally at least one element (metal) selected from groupVIB and/or group VIII (group 6 and groups 8, 9 and 10 in the newnotation for the periodic table), preferably molybdenum, tungsten,cobalt, nickel or iron. The catalyst also optionally comprises at leastone element from group VIIA (group 17 in the new notation for theperiodic table), for example fluorine.

The present invention also relates to a catalyst for hydrocrackinghydrocarbon feeds, said catalyst comprising at least one beta zeolite,at least one matrix selected from the group formed by mineral matrices,preferably oxide type mineral matrices, preferably amorphous or of lowcrystallinity and generally porous, at least one mixed sulphide phasecomprising sulphur and at least one element from group VB of theperiodic table (group 5 in the new notation of the periodic table:“Handbook of Chemistry and Physics”, 76^(th) edition, 1995-1996, insidefront cover), such as tantalum, niobium or vanadium, preferably niobium,and at least one element from group VIB of the periodic table (group 6)such as chromium, molybdenum or tungsten, more preferably molybdenum.The catalyst can also optionally comprise at least one metal from groupVIII of the periodic table (groups 8, 9 and 10), such as iron, cobalt,nickel, ruthenium, osmium, rhodium, iridium, palladium, platinum, andoptionally at least one element selected from the group formed bysilicon, boron or phosphorous, and optionally at least one element fromgroup VIIA of the periodic table (group 17), such as fluorine, chlorine,bromine or iodine, preferably fluorine.

The present invention also relates to processes for preparing saidcatalyst, and to its use for hydrocracking hydrocarbon feeds such aspetroleum cuts, cuts originating from coal containing aromatic compoundsand/or olefinic compounds and/or naphthenic compounds and/or paraffiniccompounds, the feeds possibly containing metals and/or nitrogen and/oroxygen and/or sulphur.

Hydrocracking heavy petroleum feeds is a very important refining processwhich produces lighter fractions such as gasoline, jet fuel and lightgas oil from surplus heavy feeds, which lighter fractions are needed bythe refiner to enable production to be matched to demand. Somehydrocracking processes can also produce a highly purified residue whichcan constitute an excellent base for oils. The advantage of catalytichydrocracking over catalytic cracking is that it can provide very goodquality middle distillates, jet fuels and gas oils. The gasolineproduced has a much lower octane number than that resulting fromcatalytic cracking.

All catalysts used for hydrocracking are bifunctional, combining an acidfunction and a hydrogenating function. The acid function is supplied bylarge surface area supports (150 to 800 m²/g in general) with asuperficial acidity, such as halogenated aluminas (in particularfluorinated or chlorinated), combinations of boron and aluminium oxides,amorphous silica-aluminas and clays. The hydrogenating function issupplied either by one or more metals from group VIII of the periodictable, such as iron, cobalt, nickel, ruthenium, rhodium, palladium,osmium, iridium or platinum, or by a combination of at least one metalfrom group VI of the periodic table, such as molybdenum or tungsten, andat least one group VIII metal.

The equilibrium between the two, acid and hydrogenating, functions isthe fundamental parameter which governs the activity and selectivity ofthe catalyst. A weak acid function and a strong hydrogenating functionproduces low activity catalysts which generally operate at a hightemperature (390° C. or above), and at a low supply space velocity (HSV,expressed as the volume of feed to be treated per unit volume ofcatalyst per hour, and is generally 2 or less), but have very goodselectivity for middle distillates. In contrast, a strong acid functionand a weak hydrogenating function produces very active catalysts butselectivities for middle distillates are poor. The search for suitablecatalysts thus revolves around the proper selection of each of thefunctions to adjust the activity/selectivity balance of the catalyst.

Thus one of the great interests of hydrocracking is to have a highdegree of flexibility at various levels: flexibility as regards thecatalysts used, which provides flexibility in the feeds to be treatedand in the products obtained. One parameter which is easily mastered isthe acidity of the catalyst support.

The vast majority of conventional hydrocracking catalysts areconstituted by low acidity supports such as amorphous silica-aluminas.These systems are more particularly used to produce very high qualitymiddle distillates and again, when their acidity is very low, base oils.

Amorphous silica-aluminas are low acidity supports. Many of thecatalysts in the hydrocracking industry are based on silica-aluminaassociated either with a group VIII metal or, as is preferably when theheteroatomic poison content in the feed to be treated exceeds 0.5% byweight, a combination of sulphides of group VIB and VIII metals. Thesesystems have very good selectivity for middle distillates, and goodquality products are formed. The least acid of such catalysts can alsoproduce lubricating bases. The disadvantage of all of such catalyticsystems based on an amorphous support is, as has been stated, their lowactivity; Further, simple sulphides of group VB elements have beendescribed as constituents for catalysts for hydrorefining hydrocarbonfeeds, such as by niobium trisulphide in U.S. Pat. No. 5,294,333.Mixtures of simple sulphides comprising at least one group VB elementand a group VIB element have also been tested as constituents forcatalysts for hydrorefining hydrocarbon feeds as described, for example,in U.S. Pat. No. 4,910,181 or U.S. Pat. No. 5,275,994.

The research carried out by the Applicant on zeolites and on activehydrogenating phases have led the Applicant to the discovery that,surprisingly, catalysts for hydrocracking hydrocarbon feeds comprising:

either at least one amorphous or low crystallinity matrix which isgenerally porous such as alumina, at least one element from group VB ofthe periodic table, such as tantalum, niobium or vanadium, preferablyniobium, at least one beta zeolite, at least one promoter elementselected from the group formed by boron, phosphorous and silicon;

or at least one matrix selected from the group formed by mineralmatrices, preferably oxide type mineral matrices, preferably amorphousor of low crystallinity and generally porous such as alumina, at leastone beta zeolite, and at least one mixed sulphide phase. This catalystcan also optionally comprise at least one element from group VIII,optionally an element selected from the group formed by silicon,phosphorous and boron, and optionally at least one element selected fromgroup VIIA.

The catalyst of the invention comprises at least one beta zeolite whichis preferably at least partially in its hydrogen form. The term “betazeolite” means zeolites with a BEA structure type as described in the“Atlas of Zeolite Structure Types”, W. M Meier, D. H. Olson and Ch.Baerlocher, 4^(th) revised edition, 1996, Elsevier.

The catalyst also comprises at least one element from group VIB of saidperiodic table such as chromium, molybdenum and tungsten, preferablymolybdenum or tungsten, more preferably still molybdenum, optionally agroup VIII element i.e., an element selected from the group formed by:Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, preferably iron, cobalt, nickel orruthenium, and optionally a group VIIA element, preferably fluorine. Thecatalyst has a higher hydrocracking activity than those of known priorart catalytic formulae based on a group VIB element.

The mixed sulphide optionally present in the catalyst of the inventionis characterized by the following approximate general formula:

A_(x)B_(1-x)S_(y)

where:

x is a number in the range 0.001 to 0.999, preferably in the range 0.005to 0.995, more preferably 0.05 to 0.95;

y is a number in the range 0.1 to 8, preferably in the range 0.1 to 6,more preferably 0.5 to 4;

A is a group VB element such as tantalum, niobium or vanadium,preferably niobium;

B is an element selected from group VIB such as chromium, molybdenum ortungsten, preferably molybdenum or tungsten, more preferably molybdenum.

The catalyst of the invention can be in a supported form, i.e.,comprising at least one support constituted by at least one matrix, forexample an oxide type matrix, for example alumina, and at least one betazeolite.

The catalyst of the present invention can generally comprise, in % byweight with respect to the total catalyst mass:

0.1% to 99.8%, preferably 0.1% to 90%, more preferably 0.1% to 80%,still more preferably 0.1% to 70% of at least one beta zeolite;

0.1% to 60%, preferably 0.1% to 50%, and more preferably 0.1% to 40%, ofat least one element selected from group VB;

0.1% to 99%, preferably 1% to 99%, of at least one porous amorphous orlow crystallinity oxide type mineral matrix;

0.1% to 20%, preferably 0.1% to 15%, more preferably 0.1% to 10%, of atleast one promoter element selected from the group formed by boron,phosphorous and silicon, not including the silicon which may becontained in the zeolite;

the catalyst also possibly comprising:

0 to 60%, preferably 0.1% to 50%, more preferably 0.1% to 40%, of atleast one element selected from elements from group VIB and group VIII;and

0 to 20%, preferably 0.1% to 15%, more preferably 0.1% to 10%, of atleast one element selected from group VIIA, preferably fluorine.

When it is present, the promoter element silicon is in the amorphousform and principally located on the matrix. The group VB, VIB and VIIIelements in the catalyst of the present invention can be partially orcompletely present in the metallic and/or oxide and/or sulphide form.

When it contains a mixed sulphide phase, the catalyst of the presentinvention generally comprises, in % by weight with respect to the totalcatalyst mass:

0.1% to 99.9%, preferably 1% to 99.5%, more preferably 5% to 99.0%, ofat least one matrix, preferably an oxide type matrix, preferablyamorphous or of low crystallinity and generally porous;

0.1% to 99.8%, preferably 0.1% to 90%, more preferably 0.1% to 80%,still more preferably 0.1% to 70%, of at least one beta zeolite, with anoverall silicon/aluminium (Si/Al) atomic ratio which is preferablyhigher than about 10, more preferably in the range 10 to 200, and morepreferably still in the range 10 to 150;

0.1% to 99.5%, preferably 0.5% to 99%, more preferably 1% to 90%, of atleast one mixed sulphide of at least one group VB element and at leastone group VIB element;

the catalyst possibly further containing:

0 to 30%, preferably 0 to 25%, more preferably 0.1% to 20%, of at leastone group VIII metal;

0 to 20%, preferably 0 to 15%, more preferably 0.1% to 15%, of at leastone element selected from the group formed by boron, phosphorous andsilicon; and

0 to 15%, preferably 0.1% to 15%, more preferably 0.1% to 10%, of atleast one element selected from group VIIA, preferably fluorine.

The matrix is preferably selected from the group formed by mineralmatrices, preferably porous mineral matrices, preferably amorphous or oflow crystallinity, preferably an oxide type matrix.

The mixed sulphide is generally identified from an X ray diffractiondiagram. It can also be identified from determining the metal-metaldistance measured by an X ray absorption technique or Extended X rayAbsorption Fine Structure (EXAFS). As an example, for a mixed sulphideof molybdenum and niobium, EXAFS identification determines theniobium-niobium distances or the niobium-molybdenum distances if theEXAFS analysis is carried out using the niobium K edge. It can alsodetermine the molybdenum-molybdenum and molybdenum-niobium distances ifthe EXAFS analysis is carried out using the molybdenum K edge.

The X ray diffraction diagram was obtained using an INEL diffractometerwith a curved multidetector using a conventional powder technique withthe monochromatic K alpha 1 line of copper. From the position of thediffraction peaks represented by the angle 2 theta, the Braggrelationship is used to calculate the characteristic interplanardistances d_(hkl) of the sample and the lattice parameters of the mixedphase a and c in Å (1 Å=1 Angström=10⁻¹⁰ m). The lattice parameter “a”represents the average metal-metal distance between two neighbouringions and is characteristic of the existence of a mixed phase. Thestructural type can also be determined by diffraction. Thus, forexample, for a mixed sulphide of molybdenum and niobium, simplesulphides of Mo and Nb, MoS₂ and NbS₂, both exist in the form of twostructural types, the hexagonal form 2s and the rhombohedral form 3s.For molybdenum-rich samples (x<0.5), the mixed phase tends tocrystallise in the hexagonal type structure 2s and the latticeparameters vary linearly as a function of the proportion of niobium inthe mixed phase as shown in Table 1. For niobium-rich samples (x>=0.5),the mixed phase tends to crystallise in the rhombohedral structure 3sand the lattice parameters also vary linearly as a function of theniobium composition as shown in Table 2.

The error in the measurement of delta (d_(hkl)) can be estimated as afunction of the absolute error in the measurement of angle 2 theta,using the Bragg relationship. An absolute error delta(2theta) of ±0.05°is normally acceptable. The intensity I_(rel) at each value of d_(hkl)is measured from the surface area of the corresponding diffraction peak.

TABLE 1 Phase a (Å) c (Å) MoS₂-2s 3.16 12.29 Nb_(0.2)Mo_(0.8)S₂ 3.2012.05 Nb_(0.3)Mo_(0.5)S₂ 3.22 12.02 Nb_(0.4)Mo_(0.6)S₂ 3.25 12.00NbS₂-2s 3.31 11.89

TABLE 2 Phase a (Å) c (Å) MoS₂-2s 3.16 18.37 Nb_(0.6)Mo_(0.4)S₂ 3.2518.00 Nb_(0.7)Mo_(0.3)S₂ 3.27 17.98 Nb_(0.8)Mo_(0.2)S₂ 3.30 17.97NbS₂-2s 3.33 17.81

Analysis of the X ray diffraction diagram in the form of the latticeparameters shown in Tables 1 and 2 leads to identification of the mixedniobium and molybdenum sulphide.

EXAFS analysis was carried out at the niobium K edge using synchrotronradiation between 18850 and 19800 eV measuring the absorbed intensityusing a powder sample deposited on an adhesive strip. The absorptionspectrum was analysed using an established procedure (F. W. Lyttle, D.E. Sayers and E. A Stern, Physical Review B, vol 11, page 4825, 1975 andE. A. Stem, D. E. Sayers and F. W. Lyttle, Physical Review B, vol 11,page 4836) which allowed the interatomic distances to be determined.

Analysis of the X ray absorption spectrum led to a deduction of a radialdistribution function. This radial distribution showed a first peakrelative to the sulphur environment of the niobium the maximum positionof which gave the niobium-sulphur distance or R1 as generally 2.45 Å to2.48 Å, typical of NbS₂. On this radial distribution a second peak couldbe seen which corresponded to the second co-ordination sphere of theniobium composed of niobium or molybdenum atoms which could not bedistinguished because of their very close atomic numbers, the positionof the maximum of which gave the average metal-metal distance R2(niobium-niobium or niobium-molybdenum), which value varies as afunction of the composition of the mixed phase as shown in Table 3; thatvalue is between the niobium-niobium distance in NbS₂ (3.33 Å) and themolybdenum-molybdenum distance in MoS₂ (3.16 Å), and is generally anaverage of 3.20 to 3.35 Å. This distance agrees with the distances adetermined by X ray diffraction and varies with the composition of themixed phase. The distances reported in Table 3 are corrected for phaseoffset and can thus be compared with the data obtained by X raydiffraction. Determination of interatomic metal-metal distances by EXAFSis very accurate since the absolute error estimated for the distance is±0.02 Å.

TABLE 3 Phase R3 (Å) R2 (Å) Nb_(0.2)Mo_(0.8)S₂ 2.46 3.20Nb_(0.3)Mo_(0.7)S₂ 2.45 3.22 Nb_(0.4)Mo_(0.6)S₂ 2.48 3.27Nb_(0.6)Mo_(0.4)S₂ 2.47 3.28 Nb_(0.7)Mo_(0.3)S₂ 2.47 3.30Nb_(0.8)Mo_(0.2)S₂ 2.48 3.31 NbS₂ 2.48 3.33

The catalysts of the invention can be prepared using any of the methodsknown to the skilled person.

A first preferred process for preparing the catalyst of the presentinvention comprises the following steps:

a) drying and weighing a solid termed the precursor, comprising at leastthe following compounds: at least one matrix, at least one beta zeolite,optionally at least one promoter element selected from the group formedby boron, phosphorous and silicon, optionally at least one elementselected from group VIB and group VIII elements, optionally at least oneelement from group VIIA, this preferably being formed;

b) the dry solid obtained in step a) is calcined at a temperature of atleast 150° C., preferably at least 450° C.;

c) the solid precursor defined in step b) is impregnated with a solutioncontaining at least one group VB element, preferably niobium;

d) the moist solid is left in a humid atmosphere at a temperature in therange 10° C. to 120° C.;

e) the moist solid obtained in step d) is dried at a temperature in therange 60° C. to 150° C.;

f) the dried solid from step e) is calcined in dry air at a temperatureof at least 150° C., preferably at least about 250° C.

The solid obtained from any one of steps a) to e) can be impregnatedwith at least one solution containing all or at least a portion of theelement selected from the group VIB and group VIII elements, optionallyat least one promoter element selected from the group formed by boron,phosphorous and silicon and optionally at least one group VIIA element.

The precursor of step a) above can be prepared using any of theconventional methods known to the skilled person. In a preferredpreparation process, the precursor is obtained by mixing at least onematrix and at least one beta zeolite, then is formed, dried andcalcined. The promoter element or elements selected from the groupformed by boron, phosphorous and silicon, that or those selected fromelements from groups VIB, VIII and/or from group VIIA elements, are thenintroduced by any method which is known to the skilled person, at anyone of steps a) to e), before or after forming and before or aftercalcining the mixture.

Forming can be carried out, for example, by extrusion, pelletisation,using the oil-drop method, by rotating plate granulation or by any othermethod which is known to the skilled person. At least one calcining stepcan be carried out after any one of the preparation steps; it isnormally carried out in air at a temperature of at least 150° C.,preferably at least 300° C. Thus the product obtained from step a)and/or step e) and/or after optional introduction of the element orelements selected from the elements from groups VIB, VIII and/or frompromoter elements from the group constituted by boron, phosphorous andsilicon, and/or from group VIIA elements, is then optionally calcined inair, usually at a temperature of at least 150° C., preferably at least250° C., more preferably between about 350° C. and 1000° C.

The hydrogenating element can be introduced at any step in thepreparation, preferably during mixing, or more preferably after forming.Forming is followed by calcining; the hydrogenating element isintroduced before or after this calcining step. In all cases, thepreparation is finished by calcining at a temperature of 250° C. to 600°C. One preferred method in the present invention consists of mixing atleast one zeolite in a moist alumina gel for several tens of minutes,then passing the paste obtained through a die to form extrudates with adiameter in the range 0.4 to 4 mm. The hydrogenating function can thenbe introduced only in part (for example, when using combinations ofoxides of group VIB and VIII metals) or completely at the moment ofmixing the zeolite, i.e., at least one beta zeolite, with at least onegel of the oxide selected as the matrix. It can be introduced by one ormore ion exchange operations carried out on the calcined supportconstituted by at least one zeolite dispersed in at least one matrix,using solutions containing precursor salts of the selected metals whenthese are group VIII metals. It can be introduced by one or moreoperations for impregnating the formed and calcined support, using, asolution of precursors of oxides of metals from group VIII (inparticular cobalt and nickel) when the precursors of the oxides of groupVIB metals (in particular molybdenum or tungsten) have previously beenintroduced on mixing the support. Finally, it can be introduced by oneor more impregnation operations carried out on the calcined supportconstituted by at least one beta zeolite and at least one matrix, usingsolutions containing precursors of oxides of groups VIB and/or VIIImetals, the precursors of the oxides of the group VIII metals preferablybeing introduced after those of group VIB or at the same time as thelatter.

A further preferred preparation process consists of introducing at leastone group VB element and at least one element selected from group VIIIand group VIB elements into a mixture of at least one matrix with atleast one beta zeolite, before or after forming and before or aftercalcining said mixture.

Preferably, the support is impregnated with an aqueous solution. Thesupport is preferably impregnated using the incipient wetnessimpregnation method which is well known to the skilled person.Impregnation can be carried out in a single step using a solutioncontaining all of the constituent elements of the finished catalyst.

The boron and/or phosphorous and/or silicon and the optional elementselected from group VIIA, the halide ions, preferably fluorine, can beintroduced into the catalyst at a variety of stages of the preparationusing any technique which is known to the skilled person.

One preferred method of the invention consists of depositing, forexample by impregnation, the selected promoter element or elements, forexample boron-silicon, onto the calcined or uncalcined precursor,preferably the calcined precursor. To this end, an aqueous solution ofat least one boron salt such as ammonium biborate or ammoniumpentaborate is prepared in an alkaline medium and in the presence ofhydrogen peroxide and dry impregnation is carried out, in which the porevolume of the precursor is filled with the solution containing boron.When silicon is deposited, for example, a solution of a silicone typesilicon compound is used.

The boron and silicon can also be deposited simultaneously using, forexample, a solution containing a boron salt and a silicone type siliconcompound. Thus, for example in the case where the precursor is anickel-molybdenum type catalyst supported on alumina and the zeolite isselected from the group formed by beta zeolites, it is possible toimpregnate this precursor with an aqueous solution of ammonium biborateand Rhodorsil E1P silicone from Rhone Poulenc, to dry, for example at80° C., then to impregnate with a solution of ammonium fluoride, to dry,for example at 80° C., and to calcine, for example and preferably in airin a traversed bed, for example at 500° C. for 4 hours. The group VBelement is then deposited using any method known to the skilled person.

The promoter element selected from the group formed by boron,phosphorous and silicon, and the element selected from the halogens ofgroup VIIA, can also be introduced by one or more impregnationoperations, for example using an excess of solution, carried out on thecalcined precursor.

Thus, for example, it is possible to impregnate the precursor with anaqueous solution of ammonium biborate and/or Rhodorsil EP1 silicone fromRhone Poulenc, to dry at 80° C., for example, then to impregnate with anammonium fluoride solution, to dry, for example at 80° C., and then tocalcine, for example and preferably in air in a traversed bed, forexample at 500° C. for 4 hours. Then the group VB element is depositedusing any method which is known to the skilled person.

Other impregnation sequences can be carried out to obtain the catalystof the present invention.

As an example, it is possible to impregnate the precursor with asolution containing the promoter elements (B, P, Si), to dry, to calcinethen to impregnate the solid obtained with the solution containing afurther promoter element, to dry, then to calcine. It is also possibleto impregnate the precursor with a solution containing two promoterelements, to dry, to calcine then to impregnate the solid obtained withthe solution containing the other promoter element, to dry, and then tocarry out the final calcining step. The group VB element is thendeposited using any method which is known to the skilled person.

Niobium impregnation can be facilitated by adding oxalic acid andpossibly ammonium oxalate to the niobium oxalate solutions. Othercompounds can be used to improve solubility and facilitate impregnationof the niobium, as is well known to the skilled person.

Sulphurisation can be carried out using any method which is known to theskilled person. The preferred method of the invention consists ofheating the uncalcined catalyst in a stream of a hydrogen-hydrogensulphide mixture or in a stream of a nitrogen-hydrogen sulphide mixtureor in pure hydrogen sulphide at a temperature in the range 150° C. to800° C., preferably in the range 250° C. to 600° C., generally in atraversed bed reaction zone.

When it contains a mixed sulphide phase, the catalyst of the inventioncan be prepared either by firstly preparing the bulk mixed sulphidephase and then depositing it on a support, or by directly generating aprecursor of the catalyst consisting of a supported mixed sulphidephase. The optional elements which may be present (group VIII elements,elements selected from the group formed by silicon, phosphorous andboron, group VIIA elements) can be introduced at any stage of thepreparation, for example during preparation of the bulk or supportedmixed sulphide phase, or to the support alone.

A preferred process for preparing the bulk mixed sulphide comprised inthe catalyst of the present invention comprises the following steps:

a) forming a reaction mixture which comprises at least the followingcompounds: at least one source of a group VB element, at least onesource of a group VIB element, optionally water, optionally at least onesource of an element selected from the group formed by group VIIIelements, optionally at least one source of an element selected from thegroup formed by silicon, phosphorous and boron, and optionally anelement selected from the halogens, i.e., group VIIA elements,preferably fluorine;

b) maintaining said mixture at a heating temperature which is generallyover about 40° C., at a pressure which is at least equal to atmosphericpressure and in the presence of a sulphur compound until the mixedsulphide is obtained.

The mixture formed in step a) above can be produced simultaneously orsuccessively, in any order, in the same physical space or separately.

Step b) has proved to be very difficult to carry out in the majority ofconventional sulphurisation processes which are known to the skilledperson.

The sulphurisation of solids containing at least one group VB element inthe oxide form has been proved to be very difficult to carry out in themajority of conventional sulphurisation processes which are known to theskilled person. Catalysts containing at least one group VB elementsupported on an alumina type matrix are known to be very difficult tosulphurise once the group VB element/matrix combination had beencalcined at a temperature of over 200° C.

One preferred method of the invention consists of not calcining thecatalyst and of sulphurising using a gaseous compound comprisingsulphur, such as CS_(2,) in a pressurised autoclave. Thus a preferredmethod of the invention consists of sulphurising a mixture, generally inthe form of powdered solids, at a temperature in the range 40° C. to700° C., preferably in the range 60° C. to 500° C., under autogenouspressure and in the presence of a gaseous sulphur compound, preferablyCS₂.

An autoclave is preferably used which is internally lined with apolymeric material, generally polytetrafluoroethylene, at a temperatureof over 100° C. The heating period for the reaction mixture which isnecessary for sulphurising depends on the composition of the reactionmixture and the reaction temperature. Such a method, described in theliterature for the synthesis of a catalyst comprising niobium sulphideon alumina (Journal of Catalysis, vol. 156, pages 279-289 (1995)) and inEuropean patent EP-A-0 440 516 for the synthesis of a binary sulphurcompound, i.e., a simple sulphide comprising sulphur and anotherelement, a transition metal or a rare earth, has been found to besuitable for the synthesis of the mixed sulphides of the presentinvention.

The supported catalysts of the present invention can be prepared usingany of the methods which are known to the skilled person. A number ofthese processes are described below.

In general, it is possible to mechanically mix the beta zeolite andmatrix generally in the form of powder with any precursor of the mixedsulphide phase, then sulphurising, as will be described in more detailbelow. It is also possible to produce a mechanical mixture comprisingthe mixed sulphide powder, synthesised using one of the methodsdescribed above, and a support (i.e., a mixture of matrix and zeolite)also in the form of a powder, then optionally to form.

In all cases it is possible a priori to add the optional elementspresent in the supported catalyst of the invention at any stage of thepreparation, using methods which are known to the skilled person.

One process for preparing a supported mixed sulphide phase comprised inthe catalyst of the present invention comprises the following steps:

a) forming a reaction mixture which comprises at least the followingcompounds: at least one matrix selected from the group formed by mineralmatrices, preferably oxide type matrices, preferably amorphous or of lowcrystallinity and generally porous, at least one beta zeolite, at leastone source of a group VB element, at least one source of a group VIBelement, optionally water, optionally at least one element selected fromthe group formed by group VIII elements, optionally at least one sourceof an element selected from the group formed by silicon, phosphorous andboron, and optionally at least one source of an element selected fromthe halogens, i.e., group VIIA elements, preferably fluorine;

b) maintaining said mixture at a heating temperature which is generallyover about 40° C., in the presence of a sulphur compound until a solidcontaining at least one matrix, at least one beta zeolite and at leastone mixed sulphide phase is obtained.

Step a) is preferably a support impregnation step.

Thus, for example in the preferred case when the group VB metal isniobium and the group VIB metal is molybdenum, the support (comprisingthe matrix and the zeolite), or the matrix alone, for example alumina,can be impregnated using ammonium heptamolybdate, then dried at 80° C.,then impregnated with niobium oxalate, dried at 80° C., thensulphurised, for example and preferably using CS₂ in an autoclave underautogenous pressure, as described for the preparation of the bulk mixedsulphide phase, at 400° C. for 10 hours, for example.

It is also possible to form the mixture of powders comprising the sourceof the group VB element, the source of the group VIB element, theoptional water, the optional source of the element selected fromsilicon, phosphorous and boron, the optional source of the group VIIAelement and the optional sulphur source and then to impregnate thesupport. It is also possible to impregnate the matrix alone and then toadd the beta zeolite, using any means which is known to the skilledperson, for example by mechanical mixing.

When the matrix impregnated, the matrix is preferably impregnated usingthe “dry” impregnating method which is well known to the skilled person.Impregnation can be carried out in a single step using a solutioncontaining all of the constituent elements of the final catalyst.

The supported catalyst of the invention can be formed by extrusion,pelletisation, the oil-drop method, rotating plate granulation or anyother method which is known to the skilled person. The pre-formedsupport is optionally calcined in air, usually at a temperature of atleast 300° C., routinely at about 350° C. to 1000° C.

The mixed sulphide, also the group VIII element, also the elementselected from the group formed by P, B and Si and the element selectedfrom group VIIA, the halogens, preferably fluorine, can be introducedinto the catalyst at various stages in the preparation and in variousmanners.

The mixed sulphide phase can be introduced only in part (for examplewhen at least one group VB metal and/or group VIB metal is combined withat least one group VIII metal) or completely on mixing the poroussupport, optionally with all or part of the zeolite.

The group VIII metal, also the element selected from the group formed byP, B, and Si and the element selected from the halogens of group VIIAcan be introduced using one or more ion exchange operations carried outon the calcined matrix constituted by the mixed sulphide dispersed inthe selected support, using a solution containing at least one precursorsalt of the group VIII metal. It can be introduced by at least oneoperation for impregnating the formed and calcined support, using asolution of a precursor of at least one group VIII metal (in particularcobalt and/or nickel), any group VIII metal precursor preferably beingintroduced at the same time or after any group VB and VIB metalprecursor.

When the metals are introduced in a number of impregnation steps usingthe corresponding precursor salts, an intermediate drying step for thecatalyst is generally carried out at a temperature which is generally inthe range 60° C. to 200° C.

The catalyst of the present invention can comprise an element (metal)from group VIII such as iron, cobalt, nickel, ruthenium, rhodium,palladium, osmium, iridium or platinum. Preferred group VIII elementsare an element selected from the group formed by iron, cobalt, nickeland ruthenium. Advantageously, combinations of the following elementsare used: nickel-niobium-molybdenum, cobalt-niobium-molybdenum,iron-niobium-molybdenum, nickel-niobium-tungsten,cobalt-niobium-tungsten, iron-niobium-tungsten; preferred combinationsare: nickel-niobium-molybdenum, cobalt-niobium-molybdenum. It is alsopossible to use combinations of four elements, for examplenickel-cobalt-niobium-molybdenum. Combinations containing a noble metalcan also be used, such as ruthenium-niobium-molybdenum, orruthenium-nickel-niobium-molybdenum.

When the elements are introduced in a plurality of steps forimpregnating the corresponding salts, an intermediate catalyst calciningstep generally has to be carried out at a temperature in the range 250°C. to 600° C. molybdenum impregnation can be facilitated by addingphosphoric acid to ammonium paramolybdate solutions, which alsointroduces phosphorous so as to improve the catalytic activity. Otherphosphorous compounds can be used, as is well known to the skilledperson.

The porous mineral matrix, normally amorphous or of low crystallinity,is in general constituted by at least one refractory oxide in anamorphous or low crystallinity form. Said matrix is normally selectedfrom the group formed by alumina, silica, silica-alumina, or a mixtureof at least two of the above oxides. Aluminates can also be used. It ispreferable to use matrices containing alumina, in all of its forms whichare known to the skilled person, for example gamma alumina.

Sources of the group VB element which can be used are well known to theskilled person. As an example, among the niobium sources, it is possibleto use oxides such as diniobium pentoxide Nb₂O₅, niobic acid Nb₂O₅·H₂O,niobium hydroxides and polyoxoniobates, niobium alkoxides with formulaNb(OR₁)₃ where R₁ is an alkyl radical, niobium oxalate NbO(HC₂O₄)₅,ammonium niobate. Preferably, niobium oxalate or ammonium niobate areused.

Normally, beta zeolites with a total silicon/aluminium (Si/Al) atomicratio of more than about 10 are preferably used, more preferably betazeolites with an Si/Al ratio in the range 10 to 200, and still morepreferably in the range 10 to 150. These beta zeolites can be obtainedthrough synthesis or by using any post-synthesis dealumination techniqueknown to the skilled person.

Beta zeolites are advantageously used which are either entirely in thehydrogen form, or possibly partially exchanged with metal cations, forexample cations of alkali metals or alkaline-earth metals and/or cationsof rare earth metals with an atomic number of 57 to 71 inclusive(“Zeolite Molecular Sieves: Structure, Chemistry and Uses”, D. W. Breck,J. Wiley & Sons, 1973). The cation/Al atomic ratio is less than 0.8,preferably less than 0.5 and more preferably less than 0.1. Preferredbeta zeolites of the invention have specific surface areas, determinedusing the BET method, of more than 400 m²/g, preferably in the rangeabout 450 to 850 m²/g.

The sulphur source can be elemental sulphur, carbon disulphide, hydrogensulphide, sulphur-containing hydrocarbons such as dimethyl sulphide,dimethyldisulphide, mercaptans, thiophene compounds, thiols,polysulphides such as ditertiononylpolysulphide or TPS-37 from ATOCHEM,petroleum cuts which are rich in sulphur such as gasoline, kerosene, orgas oil, used alone or mixed with one of the sulphur-containingcompounds cited above. The preferred sulphur source is carbon sulphideor hydrogen sulphide.

The preferred phosphorous source is orthophosphoric acid H₃PO₄, but itssalts and esters such as ammonium phosphates are also suitable.Phosphorous can, for example, be introduced in the form of a mixture ofphosphoric acid and a basic organic compound containing nitrogen such asammonia, primary and secondary amines, cyclic amines, compounds of thepyridine family and quinolines and compounds from the pyrrole family.

A number of silicon sources can be used. Thus the following can be used:ethyl orthosilicate Si(OEt)₄, siloxanes, polysiloxanes, silicones,silicone emulsions or silicates of halides such as ammoniumfluorosilicate (NH₄)₂SiF₆ or sodium fluorosilicate Na₂SiF₆.Silicomolybdic acid and its salts, silicotungstic acid and its salts canalso advantageously be used. Silicon can be added, for example, byimpregnating with ethyl silicate in solution in an alcohol/watermixture. The silicon can also be added, for example, by impregnationwith a silicone type silicon compound suspended in water.

The boron source can be boric acid, preferably orthoboric acid H₃BO₃,ammonium biborate or pentaborate, boron oxide, or boric esters. Boroncan, for example, be introduced in the form of a mixture of boric acid,hydrogen peroxide and a basic organic compound containing nitrogen, suchas ammonia, primary and secondary amines, cyclic amines, pyridine groupcompounds, quinolines, and pyrrole group compounds. Boron can, forexample, be introduced using a solution of boric acid in a water/alcoholmixture.

Sources of group VIIA elements which can be used are known to theskilled person. As an example, fluoride ions can be introduced in theform of hydrofluoric acid or its salts. These salts are of alkalinemetals, ammonium salts or salts of an organic compound. In the lattercase, the salt is advantageously formed in the reaction mixture byreaction between the organic compound and hydrofluoric acid.Hydrolysable compounds which can liberate fluoride ions in the water canalso be used, such as ammonium fluorosilicate (NH₄)₂SiF₆, silicontetrafluoride SiF₄ or sodium fluorosilicate Na₂SiF₆. Fluorine can beintroduced, for example, by impregnating with an aqueous solution ofhydrofluoric acid or ammonium fluoride.

Sources of group VIB elements which can be used are well known to theskilled person. Examples of molybdenum and tungsten sources are oxidesand hydroxides, molybdic acids and tungstic acids and their salts, inparticular ammonium salts such as ammonium molybdate, ammoniumheptamolybdate, ammonium tungstate, phosphomolybdic acid,phosphotungstic acid and their salts, silicomolybdic acid,silicotungstic acid and their salts. Preferably, oxides and ammoniumsalts are used, such as ammonium molybdate, ammonium heptamolybdate andammonium tungstate.

Sources of group VIII elements which can be used are well known to theskilled person. As an example, non noble metals can be nitrates,sulphates, phosphates, halides (for example chlorides, bromides andfluorides), carboxylates (for example acetates and carbonates). For thenoble metals, halides (for example chlorides), nitrates, acids such aschloroplatinic acid, and oxychlorides such as ammoniacal rutheniumoxychloride can be used.

The catalysts of the present invention are formed into grains withdifferent forms and dimensions. They are generally used in the form ofcylindrical or polylobed extrudates such as bilobes, trilobes, polylobeswith a straight or twisted form, but they can also be produced and usedin the form of crushed powders, tablets, rings, beads, and wheels. Theyhave a specific surface area, measured by nitrogen adsorption using theBET method (Brunauer, Emmett, Teller, J. Am. Chem. Soc., vol. 60,309-316 (1938)), in the range about 50 to about 600 m²/g, a pore volume,measured using a mercury porosimeter, in the range about 0.2 to about1.5 cm³/g and a pore size distribution which can be unimodal, bimodal orpolymodal.

The catalysts of the present invention are used for hydrocrackinghydrocarbon feeds such as petroleum cuts. The feeds used in the processare gasolines, kerosenes, gas oils, vacuum gas oils, atmosphericresidues, vacuum residues, atmospheric distillates, vacuum distillates,heavy fuels, oils, waxes and paraffins, spent oils, deasphalted residuesor crudes, feeds from thermal or catalytic conversion processes andmixtures thereof. They contain heteroatoms such as sulphur, oxygen andnitrogen, and possibly metals.

The catalysts obtained are advantageously used for hydrocracking, inparticular vacuum distillate type heavy hydrocarbons, deasphalted orhydrotreated residues or the like. The heavy cuts are preferablyconstituted by at least 80% by volume of compounds with a boiling pointof at least 350° C., preferably in the range 350° C. to 580° C. (i.e.,corresponding to compounds containing at least 15 to 20 carbon atoms).They generally contains heteroatoms such as sulphur and nitrogen. Thenitrogen content is usually in the range 1 to 5000 ppm by weight and thesulphur content is in the range 0.01% to 5% by weight.

The hydrocracking, conditions such as temperature, pressure, hydrogenrecycle ratio, hourly space velocity, can be very variable depending onthe nature of the feed, the quality of the desired products and thefacilities available to the refiner. The temperature is generally over200° C., preferably in the range 250° C. to 480° C. The pressure is over0.1 MPa and preferably over 1 MPa. The quantity of hydrogen is a minimumof 50 and usually in the range 80 to 5000 normal liters of hydrogen perliter of feed. The hourly space velocity is generally in the range 0.1to 20 volumes of feed per volume of catalyst per hour.

The catalysts of the present invention optionally undergo sulphurisationtreatment to transform at least part of the metallic species into thesulphide before bringing them into contact with the feed to be treated.This sulphurisation activation treatment is well known to the skilledperson and can be carried out using any method which has already beendescribed in the literature, either in situ, i.e., in the hydrocrackingreactor, or ex situ.

One conventional sulphurisation method which is well known to theskilled person consists of heating, in the presence of hydrogen sulphideto a temperature in the range 150° C. to 800° C., preferably in therange 250° C. to 600° C., generally in a traversed bed reaction zone.

The catalyst of the present invention can advantageously be used forhydrocracking vacuum distillate type cuts with high sulphur and nitrogencontents, more particularly cuts with a sulphur content of over 0.1% andwith a nitrogen content of over 10 ppm.

In a first partial hydrocracking implementation, also termed mildhydrocracking, the degree of conversion is below 55%. The catalyst ofthe invention is thus used at a temperature which is generally 230° C.or more, preferably in the range 300° C. to 480° C., and more preferablyin the range 350° C. to 450° C. The pressure is generally more than 2MPa, preferably 3 MPa, and preferably less than 12 MPa, more preferablyless than 10 MPa. The quantity of hydrogen is a minimum of 100 normalliters of hydrogen per liter of feed and usually in the range 200 to3000 normal liters of hydrogen per liter of feed. The hourly spacevelocity is preferably in the range 0.15 to 10 volumes of feed pervolume of catalyst per hour. Under these conditions, the catalysts ofthe present invention have better activities for conversion,hydrodesulphurisation and hydrodenitrogenation than commerciallyavailable catalysts.

In a second implementation, the catalyst of the present invention can beused for partial hydrocracking, advantageously under moderate hydrogenpressure conditions, of cuts such as vacuum distillates containing highsulphur and nitrogen contents which have already been hydrotreated. Inthis hydrocracking mode, the degree of conversion is below 55%. In thiscase, the petroleum cut is converted in two steps, the catalysts of theinvention being used in the second step. The catalyst of the first stephas a hydrotreatment function and comprises a matrix, preferablyalumina-based, preferably containing no zeolite, and at least one metalwith a hydrogenating function. Said matrix is a porous amorphous or lowcrystallinity oxide type mineral matrix. Noon limiting examples arealuminas, silicas and silica-aluminas. Aluminates can also be used.Matrices containing alumina are preferred, in all of the forms known tothe skilled person, and more preferably aluminas, for example gammaalumina. The hydrotreatment function is ensured by at least one metal ormetal compound from group VIII, such as nickel or cobalt. A combinationof at least one metal or metal compound from group VIB (for examplemolybdenum or tungsten) and at least one metal or metal compound fromgroup VIII (for example cobalt or nickel) can be used. The totalconcentration of groups VIB and VIII metal oxides is preferably in therange 5% to 40% by weight, more preferably in the range 7% to 30% byweight, and the weight ratio, expressed as the metal oxide of the groupVIB metal (or metals) to that of the group VIII metal (or metals), is inthe range 1.25 to 20, preferably in the range 2 to 10. Further, thiscatalyst can contain phosphorous. The phosphorous content, expressed asthe concentration of phosphorous pentoxide P₂O₅, is generally at most15%, more preferably in the range 0.1% to 15% by weight, and still morepreferably in the range 0.15% to 10% by weight. It can also containboron, preferably in a ratio B/P=1.05-2 (atomic), the sum of the boron(B) and phosphorous (P) contents, expressed as the oxides, preferablybeing in the range 5% to 15% by weight.

The first step is generally carried out at a temperature of 350-460° C.,preferably 360-450° C.; at a total pressure of at least 2 MPa,preferably at least 3 MPa, an hourly space velocity in the range 0.1 to5 volumes of feed per volume of catalyst per hour, preferably in therange 0.2 to 2 volumes of feed per volume of catalyst per hour, with aquantity of hydrogen at least 100 normal liters per liter of feed,preferably 260 to 3000 normal liters per liter of feed.

In the conversion step using the catalyst of the invention (or secondstep), the temperatures are generally 230° C. or more and usually in therange 300° C. to 480° C., and preferably in the range 300° C. to 450° C.The pressure is generally at least 2 MPa and preferably at least 3 MPa.The quantity of hydrogen is a minimum of 100 normal liters of hydrogenper liter of feed and preferably in the range 200 to 3000 liters ofhydrogen per liter of feed. The hourly space velocity is preferably inthe range 0.15 to 10 volumes of feed per volume of catalyst per hour.Under these conditions, the activities of the catalysts of the presentinvention are better for conversion, hydrodesulphurisation, andhydrodenitrogenation and the selectivity for middle distillates isbetter than for commercially available catalysts. The service life ofthe catalysts is also improved in the moderate pressure range.

In a further implementation, the catalyst of the present invention canbe used for hydrocracking under high hydrogen pressure conditions, ingeneral at least 5 MPa. The treated cuts are, for example, vacuumdistillates containing high sulphur and nitrogen contents which havealready been hydrotreated. In this hydrocracking mode, the degree ofconversion is more than 55%. In this case, the petroleum cut conversionprocess is carried out in two steps, the catalyst of the invention beingused in the second step.

The catalyst of the first step has a hydrotreatment function andcomprises a matrix, preferably alumina-based, preferably containing nozeolite, and at least one metal with a hydrogenating function. Saidmatrix can also be constituted by, or comprise, a silica,silica-alumina, boron oxide, magnesia, zirconia, titanium oxide or acombination of these oxides. The hydro-dehydrogenating function isensured by at least one group VIII metal or metal compound such asnickel or cobalt. A combination of at least one metal or metal compoundfrom group VIB (in particular molybdenum or tungsten) and at least onemetal or metal compound from group VIII (in particular cobalt or nickel)can be used. The total concentration of group VIB and VIII metal oxidesis in the range 5% to 40% by weight, preferably in the range 7% to 30%by weight, and the weight ratio, expressed as the metal oxide of thegroup VIB metal (or metals) over that of the group VIII metal (ormetals), is preferably in the range 1.25 to 20, more preferably in therange 2 to 10. Further, this catalyst can contain phosphorous. Thephosphorous content, expressed as the concentration of phosphorouspentoxide P₂O₅, is at most 15%, preferably in the range 0.1% to 15% byweight, and more preferably in the range 0.15% to 10% by weight. It canalso contain boron in a ratio B/P=1.02-2 (atomic), the sum of the boron(B) and phosphorous (P) contents, expressed as the oxides, preferablybeing in the range 5% to 15% by weight.

The first step is generally carried out at a temperature in the range350° C. to 460° C., preferably in the range 360° C. to 450° C.; thepressure is at least 2 MPa, preferably at least 3 MPa; the hourly spacevelocity is in the range 0.1 to 5 volumes of feed per volume of catalystper hour, preferably in the range 0.2 to 2 volumes of feed per volume ofcatalyst per hour; and the quantity of hydrogen is at least 100 normalliters of hydrogen per liter of feed, preferably in the range 260 to3000 normal liters of hydrogen per liter of feed.

For the conversion step using the catalyst of the invention (or secondstep), the temperatures are generally 230° C. or more, usually in therange 300° C. to 480° C., and preferably in the range 330° C. to 440° C.The pressure is generally more than 5 MPa, preferably more than 7 MPa.The quantity of hydrogen is a minimum of 100 normal liters of hydrogenper liter of feed, preferably in the range 200 to 3000 liters ofhydrogen per liter of feed. The hourly space velocity is preferably inthe range 0.15 to 10 volumes of feed per volume of catalyst per hour.

Under these conditions, the activities of the catalysts of the presentinvention are better for conversion than those of commercially availablecatalysts.

The following examples illustrate the present invention without in anyway limiting its scope.

EXAMPLE 1

Preparation of a support containing a beta zeolite

Large quantities of a hydrocracking catalyst support containing a betazeolite were produced so as to enable different catalysts based on thesame support to be prepared. To this end, 18.9% by weight of a betazeolite was used which had a total Si/Al ratio (measured by X rayfluorescence) of 23.1, an atomic ratio measured by atomic adsorption ofNa/Al=0.003, a BET surface area of 720 m²/g and a pore volume of 0.298ml of liquid nitrogen/g (at the temperature of liquid nitrogen) atP/P₀=0.14, which was mixed with 81.1% by weight of a matrix composed ofultrafine tabular boehmite or alumina gel sold by Condéa Chemie GmbHunder the trade name SB3. This powder mixture was then mixed with anaqueous solution containing 66% nitric acid (7% by weight of acid pergram of dry gel) then mixed for 15 minutes. After mixing, the pasteobtained was passed through a die with cylindrical orifices with adiameter of 1.4 mm. The extrudates were dried overnight at 120° C. thencalcined at 550° C. for 2 hours in moist air containing 7.5% by volumeof water. Cylindrical extrudates 1.2 mm in diameter were obtained with aspecific surface area of 286 m²/g, a pore volume of 0.39 cm³/g and amonomodal pore size distribution centred on 11 nm. An X ray diffractionanalysis of the matrix revealed that it was composed of lowcrystallinity cubic gamma alumina with beta zeolite.

EXAMPLE 2

Preparation of hydrocracking catalysts containing a beta zeolite (not inaccordance with the invention)

Extrudates of the support containing a beta zeolite prepared in Example1 were dry impregnated with an aqueous solution of a mixture of ammoniumheptamolybdate and nickel nitrate, dried overnight at 120° C. in air andfinally calcined at 550° C. in air. The oxide weight contents ofcatalyst K (NiMo) obtained are shown in Table 1.

We impregnated a sample of catalyst NiMo with an aqueous solutioncomprising an emulsion of Rhodorsil EP1 silicone so as to deposit about1.6% by weight of SiO₂. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in dry air.Catalyst L (NiMoSi) was obtained.

Extrudates of the support containing a beta zeolite prepared in Example1 were dry impregnated with an aqueous solution of a mixture of ammoniumheptamolybdate, nickel nitrate and orthophosphoric acid, dried overnightat 120° C. in air and finally calcined at 550° C. in air. Catalyst NiMoPwas obtained.

We impregnated a sample of catalyst NiMoP with an aqueous solutioncomprising ammonium biborate and an emulsion of Rhodorsil EP1 siliconeso as to deposit about 1.7% by weight of B₂O₃ and 1.5% by weight ofSiO₂. After ageing at room temperature in a water-saturated atmosphere,the impregnated extrudates were dried overnight at 120° C. then calcinedat 550° C. for 2 hours in dry air. Catalyst M (NiMoPBSi) was obtained.

The final oxide contents of the NiMo catalysts are shown in Table 1.

TABLE 1 Characteristics of NiMo catalysts K L M Catalyst (−) (Si) (PBSi)MoO₃ (wt %) 14.2 13.9 13.2 NiO (wt %) 3.5 3.4 3.3 P₂O₅ (wt %) 0 0 4.1B₂O₃ (wt %) 0 0 1.7 SiO₂ (wt %) 15.0 16.3 15.2 Complement to 100%, 67.366.4 62.5 mainly composed of Al₂O₃ (wt %) Beta zeolite (wt %) 15.5 15.314.4

EXAMPLE 3

Preparation of hydrocracking catalysts containing a beta zeolite andniobium (in accordance with the invention)

Extrudates of the support containing a beta zeolite of Example 1 wereimpregnated with an aqueous niobium oxalate solution Nb(HC₂O₄)₅, oxalicacid and ammonium oxalate. The aqueous solution containing niobium wasprepared from 1330 ml of water in which 33 g of oxalic acid, 37.2 g ofammonium oxalate and 92.3 g of niobium oxalate had been dissolved. Toprepare the solution, the mixture of oxalic acid and ammonium oxalatewas dissolved and when the solution had become clear that solution washeated to 55° C. and niobium oxalate was added. It was then made up withwater to obtain 1330 ml of solution. The support of Example 1 was thenimpregnated using the excess method. The 1330 ml of solution was broughtinto contact with 380 g of catalyst. This deposited about 5% by weightof Nb on the catalyst. After two hours, the extrudates were recovered.These were then dried overnight at 120° C. in a stream of dry air, andfinally calcined in dry air at 550° C.

The dried extrudates were dry impregnated with an aqueous solution of amixture of ammonium heptamolybdate and nickel nitrate, dried overnightat 120° C. in air and finally calcined in air at 550° C. weight contentsof the oxides of catalyst Q (Nb) obtained are shown in Table 2.

We impregnated a sample of catalyst Q with an aqueous solutioncomprising Rhodorsil EP1 silicone emulsion so as to deposit about 1.6%by weight of SiO₂. After ageing at room temperature in a water-saturatedatmosphere, the impregnated extrudates were dried overnight at 120° C.then calcined at 550° C. for 2 hours in dry air. Catalyst R (NbSi) wasobtained

Extrudates of the support containing beta zeolite and niobium preparedabove were dry impregnated with an aqueous solution of a mixture ofammonium heptamolybdate, nickel nitrate and orthophosphoric acid, driedovernight at 120° C. then calcined in air at 550° C. Catalyst NbNiMoPwas obtained.

We impregnated a sample of catalyst NbNiMoP with an aqueous solutioncomprising ammonium biborate and Rhodorsil EP1 silicone emulsion so asto deposit about 1.7% by weight of B₂O₃ and 1.5% by weight of SiO₂.After ageing, at room temperature in a water-saturated atmosphere, theimpregnated extrudates were dried overnight at 120° C. then calcined at550° C. for 2 hours in dry air. Catalyst T (NbPBSi) was obtained.

The final oxide contents of the NbNiMo catalysts are shown in Table 2.

TABLE 2 Characteristics of NbNiMo catalysts Q R T Catalyst (Nb) (NbSi)(NbPBSi) Nb₂O₅ (wt %) 4.85 4.8 4.7 MoO₃ (wt %) 13.5 13.3 12.6 NiO (wt %)3.3 3.2 3.1 P₂O₅ (wt %) 0 0 3.9 B₂O₃ (wt %) 0 0 1.6 SiO₂ (wt %) 14.215.5 14.5 Complement to 100%, 64.1 63.1 59.5 mainly composed of Al₂O₃(wt %) Beta zeolite (wt %) 14.8 14.6 13.6

EXAMPLE 4

Preparation of a hydrocracking catalyst containing a beta zeolite and amixed sulphide phase (in accordance with the invention)

Extrudates of the support containing a beta zeolite of Example 1 weredry impregnated with an aqueous solution of a mixture of ammoniumheptamolybdate and nickel nitrate and dried overnight at 120° C. in air.The oxide weight contents of catalyst A obtained are shown in Table 3.

Catalyst A was impregnated with an aqueous niobium oxalate solutionNb(HC₂O₄)₅, oxalic acid and ammonium oxalate. The aqueous solutioncontaining niobium was prepared from 1330 ml of water in which 33 g ofoxalic acid, 37.2 g of ammonium oxalate and 92.3 g of niobium oxalatehad been dissolved. To prepare the solution, the mixture of oxalic acidand ammonium oxalate was dissolved and when the solution had becomeclear that solution was heated to 55° C. and niobium oxalate was added.It was then made up with water to obtain 1330 ml of solution. Thesupport of Example 1 was then impregnated using the excess method. The1330 ml of solution was brought into contact with 380 g of catalyst.This deposited about 5% by weight of Nb on the catalyst. After twohours, the extrudates were recovered. These were then dried overnight at120° C. in a stream of dry air. Catalyst B obtained contained, inparticular, 14.8% by weight of beta zeolite.

TABLE 3 Characteristics of catalysts (after calcining for 2 hours at500° C. in dry air) Catalyst A B C H I J Nb₂O₅ (wt %) 0 4.7 4.9 4.6 4.44.7 MoO₃ (wt %) 14.2 13.6 13.8 13.8 13.3 13.9 NiO (wt %) 3.5 3.3 3.5 3.33.2 3.3 P₂O₅ (wt %) 0 0 0 0 5.1 0 B₂O₃ (wt %) 0 0 0 0 1.6 0 SiO₂ (wt %)15.0 14.3 14.8 15.3 14.2 14.7 F (wt %) 0 0 0 0 0 1.11 Complement to100%, 67.3 64.3 63.0 63 58.2 62.3 mainly composed of Al₂O₃ (wt %) Betazeolite 15.5 14.8 14.3 14.3 13.4 14.4 (wt %)

EXAMPLE 5

Preparation of hydrocracking catalysts containing a beta zeolite and agroup VB element (not in accordance with the invention)

A hydrocracking catalyst containing a beta zeolite and niobium wassynthesised. This preparation was carried out by co-mixing a mixture ofultrafine tabular boehmite or alumina gel sold by Condéa Chemie GmbHunder the trade name SB3, a beta zeolite as described in Example 1,nickel nitrate, niobium pentoxide and ammonium heptamolybdate. To formthe paste, these sources were used so as to obtain a catalyst containing16% by weight of beta zeolite, 61.5% by weight of alumina, 14% by weightof molybdenum oxide, 3.5% by weight of nickel oxide, and 5% by weight ofniobium oxide. After mixing, the paste obtained was passed through a diewith cylindrical orifices with a diameter of 1.4 mm. The extrudates werethen dried overnight at 120° C. and calcined at 550° C. for 2 hours inmoist air containing 7.5% by volume of water. Catalyst C was obtained inthe form of cylindrical extrudates 1.2 mm in diameter, with the contentsshown in Table 1.

EXAMPLE 6

Preparation of hydrocracking catalysts containing a beta zeolite, amixed sulphide phase and at least one promoter element (in accordancewith the invention)

We impregnated a sample of catalyst A with an aqueous solutioncomprising an emulsion of Rhodorsil EP1 silicone so as to deposit about1.6% by weight of SiO₂. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in dry air.Catalyst D was obtained.

Extrudates of the support containing a beta zeolite prepared in Example1 were dry impregnated with an aqueous solution of a mixture of ammoniumheptamolybdate, nickel nitrate and orthophosphoric acid, dried overnightat 120° C. in air and finally calcined at 550° C. in air. Catalyst E wasobtained.

We impregnated a sample of catalyst E with an aqueous solutioncomprising ammonium biborate and an emulsion of Rhodorsil EP1 siliconeso as to deposit about 1.7% by weight of B₂O₃ and 1.5% by weight ofSiO₂. After ageing at room temperature in a water-saturated atmosphere,the impregnated extrudates were dried overnight at 120° C. then calcinedat 550° C. for 2 hours in dry air. Catalyst F was obtained.

A catalyst containing fluorine was also produced by impregnatingcatalyst A with a dilute hydrofluoric acid solution so as to depositabout 1% by weight of fluorine. After drying overnight at 120° C. andcalcining at 550° C. for 2 hours in dry air, catalyst G was obtained.

Catalysts D and F were then impregnated with an aqueous niobium oxalatesolution Nb(HC₂O₄)₅, oxalic acid and ammonium oxalate. The aqueoussolution containing niobium was prepared from 1330 ml of water in which33 g of oxalic acid, 37.2 g of ammonium oxalate and 92.3 g of niobiumoxalate had been dissolved. To prepare the solution, the mixture ofoxalic acid and ammonium oxalate was dissolved and when the solution hadbecome clear that solution was heated to 55° C. and niobium oxalate wasadded. It was then made up with water to obtain 1330 ml of solution.Catalysts D and F were then impregnated using the excess method. The1330 ml of solution was brought into contact with 380 g of catalyst.This deposited about 5% by weight of Nb on the catalyst. After twohours, the extrudates were recovered. These were then dried overnight at120° C. in a stream of dry air. Catalyst H was obtained from catalyst D.It contained, in particular, Nb and Si.

Catalyst I was obtained from catalyst F. In particular, it contained Nb,phosphorous, silicon and boron. Fluorine was then added to this catalystby impregnating with a dilute hydrofluoric acid solution so as todeposit about 1% by weight of fluorine. After drying overnight at 120°C. in dry air, catalyst J was obtained. The characteristics of catalystsH, I and J are shown in Table 3.

EXAMPLE 7

Comparison of sulphurised catalysts

Catalysts B, C, H, I and J prepared in the above examples weresulphurised in an autoclave under autogenous pressure in the presence ofCS₂. 20 ml of CS₂ per 100 g of catalyst was added to the autoclave, theautoclave was sealed and heated to 400° C., for 10 hours. The internalpressure was about 4 MPa. This sulphurisation step was termed S1.

Other aliquots of catalysts B, C, H, I and J prepared in the aboveexamples were sulphurised in a fixed bed reactor flushed with a streamof gas containing 15% of H₂S in nitrogen at atmospheric pressure. 2liters per hour of the mixture was passed over each 5 g of catalystwhich was heated to 600° C., for 6 hours. This sulphurisation step wastermed S2.

EXAFS analysis was carried out at the niobium K edge using synchrotronradiation between 18850 and 19800 eV by measuring the intensity absorbedby a powder sample deposited on an adhesive strip. Interatomic distancescould thus be determined. Distances R2 measured by EXAFS for the samplesof catalysts B, C, H, I and J sulphurised using method S1 and method S2respectively are shown in Table 4.

Whatever the sulphurisation method, Table 4 shows that catalystscontaining both niobium and molybdenum prepared in accordance with theinvention (B, H, I and J) have a metal-metal distance R2 in the sulphidephase which is less than that of catalyst C. The R2 value of 3.32 Å forcatalyst C indicates that in that catalyst, the niobium is in the formof a NbS₂ phase which is identical to that of a catalyst which wouldonly contain niobium alone. The metal-metal distance R2 of 3.20 Å or3.21 Å intermediate between the value for NbS₂ and MoS₂ indicates thepresence of a mixed niobium and molybdenum phase in catalysts B, H, Iand J.

TABLE 4 Catalyst Catalyst sulphurised by sulphurised by method S1 R2 (Å)method S2 R2 (Å) B-S1 3.20 B-S2 3.21 C-S1 3.32 C-S2 3.32 H-S1 3.19 H-S23.20 I-S1 3.21 I-S2 3.20 J-S1 3.21 J-S2 3.21

EXAMPLE 8

Comparison of catalysts for partial conversion hydrocracking of a vacuumgas oil

The catalysts prepared in the above Examples were employed undermoderate pressure hydrocracking conditions using a petroleum feed withthe following principal characteristics:

Density (20/4) 0.921 Sulphur (weight %) 2.46 Nitrogen (ppm by weight)1130 Simulated distillation Initial point 365° C. 10% point 430° C. 50%point 472° C. 90% point 504° C. End point 539° C. Pour point +39° C.

The catalytic test unit comprised two fixed bed reactors in upflow mode.The catalyst for the first hydrotreatment step of the process, HTH548from Procatalyse, comprising a group VI element and a group VIII elementdeposited on alumina, was introduced into the first reactor, throughwhich the feed passed first. A hydrocracking catalyst as described abovewas introduced into the second reactor, through which the feed passedlast. 40 ml of catalyst was introduced into each of the reactors. Thetwo reactors operated at the same temperature and the same pressure. Theoperating conditions of the test unit were as follows:

Total pressure 5 MPa Hydrotreatment catalyst 40 cm³ Hydrocrackingcatalyst 40 cm³ Temperature 400° C. Hydrogen flow rate 20 l/h Feed flowrate 40 cm³/h

The two catalysts underwent in-situ sulphurisation before the reaction.Once sulphurisation had been carried out, the feed described above couldbe transformed.

The catalytic performances are expressed as the gross conversion at 400°C. (GC), the gross selectivity for middle distillates (GS) and thehydrodesulphurisation (HDS) and hydrodenitrogenation (HDN) conversions.These catalytic performances were measured for the catalyst after astabilisation period, generally of at least 48 hours, had passed.

The gross conversion GC is taken to be:

GC=weight % of 380° C.^(minus) of effluent.

The 380° C.^(minus) fraction of the effluent represents the fractiondistilled at a temperature of 380° C. or less.

The gross selectivity GS for middle distillates is taken to be:

GS=100* weight of (150° C.-380° C.) fraction/weight of 380° C.^(minus)fraction of effluent.

The hydrodesulphurisation conversion HDS is taken to be:

HDS=(S_(inital) - S_(effluent))/S_(initial) * 100=(24600 -S_(effluent))/24600 * 100

The hydrodenitrogenation conversion HDN is taken to be:

HDN=(N_(initial) - N_(effluent))/N_(initial) * 100=(1130 -N_(effluent))1130 * 100

Table 5 below shows the gross conversion GC at 400° C., the grossselectivity GS, the hydrodesulphurisation conversion HDS and thehydrodenitrogenation conversion HDN for the four catalysts.

TABLE 5 Catalytic activities of catalysts for partial hydrocracking at400° C. NiMo GC GS HDS HDN catalysts (wt %) (%) (%) (%) B Nb 49.4 66.097.6 94.7 C Nb 49.4 65.2 97.0 94.2 H NbSi 50.0 65.4 97.8 95.0 J NbF 50.765.8 98.7 96.3 R NbSi 51.0 64.8 99.0 96.4 M PBSi 50.9 64.1  99.52 98.9 TNbPBSi 51.9 64.2 99.6 99.1

The results of Table 5 show that the presence of niobium and thepromoter (P, B, Si) in the catalyst containing the beta zeolite improvesthe performances for conversion without substantial reduction in thegross selectivity for middle distillates. The presence of a mixedsulphide phase (catalysts B, H and J) also improves the performancescompared with those of catalyst C which does not contain this phase.

The beta zeolite based catalysts of the invention containing a group VBelement are thus of particular interest for partial hydrocracking ofvacuum distillate type feeds containing nitrogen and in particular undermoderate hydrogen pressure.

EXAMPLE 9

Comparison of catalysts for high conversion hydrocracking of a vacuumgas oil

The catalysts prepared as described above were used under highconversion (60-100%) hydrocracking conditions. The petroleum feed was ahydrotreated vacuum distillate with the following principalcharacteristics:

Density (20/4) 0.869 Sulphur (weight %) 502 Nitrogen (ppm by weight) 10Simulated distillation Initial point 298° C. 10% point 369° C. 50% point427° C. 90% point 481° C. End point 538° C.

This feed had been obtained by hydrotreatment of a vacuum distillateusing a HR360 catalyst from Procatalyse comprising a group VI elementand a group VIII element deposited on alumina.

0.6% by weight of aniline and 2% by weight of dimethyldisulphide wereadded to the feed to simulate the partial pressures of H₂S and NH₃present in the second hydrocracking step. The prepared feed was injectedinto the hydrocracking test unit which comprised one fixed bed reactorin upflow mode, into which 80 ml of catalyst had been introduced. Thecatalyst was sulphurised using a n-hexane/DMDS+ aniline mixture at 320°C. Once sulphurisation had been carried out, the feed described abovecould be transformed. The operating conditions of the test unit were asfollows:

Total pressure 9 MPa Catalyst 80 cm³ Temperature 360-420° C. Hydrogenflow rate 80 l/h Feed flow rate 80 cm³/h

The catalytic performances are expressed as the temperature at which agross conversion of 70% is produced and by the gross selectivity for150-380° C. middle distillates. These catalytic performances weremeasured for the catalyst after a stabilisation period, generally of atleast 48 hours, had passed.

The gross conversion GC is taken to be:

GC=weight % of 380° C.^(minus) of effluent.

The gross selectivity GS for middle distillates is taken to be:

CS=100* weight of (150° C. -380° C.) fraction/weight of 380° C.^(minus)fraction of effluent.

The reaction temperature was fixed so as to obtain a gross conversion GCof 70% by weight. Table 6 below shows the reaction temperature and grossselectivity for the catalysts described above.

TABLE 6 Catalytic activities of catalysts for high conversionhydrocracking (70° C.) NiMo catalysts T (° C.) GS (%) A — 371 49.2 B Nb369 51.7 C Nb 371 49.9 J NbF 365 53.7 K — 369 51.2 T NbPBSi 364 54.1

The presence of niobium and promoter (P, B, Si) in the catalystscontaining beta zeolite improve the conversion activity, meaning areduction in the reaction temperature required for 70% conversion andimproved gross selectivity for middle distillates.

Comparison of catalysts B and C shows that the presence of a mixedsulphide phase of molybdenum and niobium in the catalyst containing abeta zeolite can substantially improve selectivity.

The catalysts of the invention are thus of particular interest for highconversion hydrocracking of a vacuum distillate type feed, in particularat a moderate hydrogen pressure.

What is claimed is:
 1. A catalyst comprising at least one beta zeolite,at least one matrix selected from the group formed by mineral matrices,at least one mixed sulphide phase comprising sulphur and at least onegroup VB element and at least one group VIB element, optionally at leastone group VIII metal and optionally at least one element selected fromthe group formed by silicon, boron and phosphorous, and optionally atleast one element from group VIIA of the periodic table.
 2. A catalystaccording to claim 1, in which the overall silicon aluminum atomic ratioof the beta zeolite is in the range 10 to
 200. 3. A catalyst accordingto claim 1, in which the group VB element is niobium.
 4. A catalystaccording to claim 1, in which the group VIB element is molybdenum ortungsten and the group VIII element is iron, cobalt or nickel.
 5. Acatalyst according to claim 1, comprising a mixed sulphide phase withthe following approximate general formula: A_(x)B_(1-x)S_(y) where: x isa number in the range 0.001 to 0.999; y is a number in the range 0.1 to8; A is a group VB element; B is an element selected from group VIB. 6.A catalyst according to claim 1, further comprising at least one elementfrom group VIII of the periodic table.
 7. A catalyst according to claim1, in which the matrix is alumina.
 8. A catalyst according to claim 1,further comprising at least one element selected from the group formedby silicon, boron and phosphorous.
 9. A catalyst according to claim 1,further comprising at least one group VIIA element.
 10. A catalystaccording to claim 1, comprising, in weight % with respect to the totalcatalyst mass: 0.1% to 99.9% of at least one matrix; 0.1% to 99.8% of atleast one beta zeolite with a lattice parameter in the range 2.424 nmand 2.455 nm and with an overall SiO₂/Al₂O₃ molar ratio of more than 8;0.1% to 99.5% of at least one mixed sulphide phase of at least one groupVB element and at least one group VIB element; 0 to 30% of at least onegroup VIII element; 0 to 20% of at least one element selected from thegroup formed by boron, phosphorous and silicon; and 0 to 15% of at leastone element selected from group VIIA.
 11. A process for preparing a bulkmixed sulphide phase comprised in the catalyst of claim 10, comprisingthe following steps: a) forming a reaction mixture which comprises atleast the following compounds: at least one source of a group VBelement, at least one source of a group VIB element, optionally water,optionally at least one element selected from the group formed by groupVIII elements, optionally at least one source of an element selectedfrom the group formed by silicon, phosphorous and boron, and optionallyan element selected from the halogens, i.e., group VIIA elements; b)maintaining said mixture at a heating temperature which is generallyover about 40° C., at a pressure which is at least equal to atmosphericpressure and in the presence of a sulphur compound until the mixedsulphide is obtained.
 12. A process for preparing a supported mixedsulphide phase comprised in the catalyst of claim 10, comprising thefollowing steps: a) forming a reaction mixture which comprises at leastthe following compounds: at least one matrix selected from the groupformed by mineral matrices, preferably oxide type mineral matrices,preferably amorphous or of low crystallinity and generally porous, atleast one beta zeolite with a lattice parameter in the range 2.424 nmand 2.455 nm, with an overall SiO₂/Al₂O₃ molar ratio of over 8, at leastone source of a group VB element, at least one source of a group VIBelement, optionally water, optionally at least one element selected fromthe group formed by group VIII elements, optionally at least one sourceof an element selected from the group formed by silicon, phosphorous andboron, and optionally at least one source of an element selected fromthe halogens, i.e., group VIIA elements; b) maintaining said mixture ata heating temperature which is generally over about 40° C., in thepresence of a sulphur compound until a solid containing at least onematrix, at least one beta zeolite and at least one mixed sulphide phaseis obtained.
 13. A process according to claim 11, in which the mixtureis sulphurised at a temperature in the range 40° C. to 700° C., underautogenous pressure, and in the presence of CS₂.
 14. A catalyst asobtained from the process of claim
 11. 15. A catalyst as obtained fromthe process of claim
 12. 16. A catalyst according to claim 1 wherein thegroup VB element is niobium, the group VIB element is molybdenum, andthe matrix is alumina.
 17. A catalyst according to claim 1 wherein thegroup VB element is niobium, the group VIB element is molybdenum, andthe group VIII element is nickel.
 18. A catalyst according to claim 1wherein the group VB element is niobium, the group VIB element ismolybdenum, and the group VIII element is cobalt.
 19. Employing acatalyst according to claim 1 in a process for hydrocracking hydrocarbonfeeds.
 20. A process according to claim 19 in which the temperature isover 200° C., the pressure is over 0.1 MPa, the quantity of hydrogen isa minimum of 50 liters of hydrogen per liter of feed, and the hourlyspace velocity is in the range 0.1 to 20 volumes of feed per volume ofcatalyst per hour.
 21. A process according to claim 19 in a mildhydrocracking process in which the degree of conversion is less than55%, in which the temperature is over 230° C., the pressure is over 2MPa and less than 12 MPa, the quantity of hydrogen is a minimum of 100liters of hydrogen per liter of feed, and the hourly space velocity isin the range 0.15 to 10 volumes of feed per volume of catalyst per hour.22. A process according to claim 19 in a hydrocracking process in whichthe degree of conversion is over 55%, in which the temperature is over230° C., the pressure is over 5 MPa, the quantity of hydrogen is aminimum of 100 liters of hydrogen per liter of feed, and the hourlyspace velocity is in the range 0.15 to 10 volumes of feed per volume ofcatalyst per hour.
 23. A process according to claim 19, in whichhydrotreatment is carried out, at a temperature in the range 350° C. to460° C., a pressure of at least 2 MPa, with a quantity of hydrogen of atleast 100 liters of hydrogen per liter of feed, and an hourly spacevelocity in the range 0.1 to 5 volumes of feed per volume of catalystper hour, this step being prior to the hydrocracking step.